Ray Optics and Optical Instruments — Physics STD 12 Science — Question

A ray of light is incident at an angle i from denser to rare medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection and the angle of refraction are respectively r and r’, then the critical angle will be

(a)

(b)

(c)

(d)

The acceleration of moon with respect to earth is 0⋅0027ms^-2 and the acceleration of an apple falling on earth's surface is about 10ms^-2. Assume that the radius of the moon is one fourth of the earth's radius. If the moon is stopped for an instant and then released, it will fall towards the earth. The initial acceleration of the moon towards the earth will be:

1. 10ms^-2
2. 0.0027ms^-2
3. 6.4ms^-2
4. 5.0ms^-2

Let n_r and n_b be the number of photons emitted by a red bulb and a blue bulb, respectively, of equal power in a given time:

1. n_r = n_b.
2. _ⁿr < n_b.
3. _ⁿr > n_b.
4. The information is insufficient to derive a relation between n_r and n_b.

Four resistances of 100 W each are connected in the form of square. Then, the effective resistance along the diagonal points is

(a) 200 W

(b) 400 W

(c) 100 W

(d) 150 W

Which of the following waves are not electromagnetic?

Total internal reflection of light is possible when light enters from

(a) Air to glass

(b) Vacuum to air

(c) Air to water

(d) Water to air

The wavelength of  X-rays produced by an X-ray tube is 0.76 Å. The atomic number of the anode material of the tube is

(a) 20

(b) 60

(c) 40

(d) 80

The pole pieces of the magnet used in a pivoted coil galvanometer are

(a) Plane surfaces of a bar magnet

(b) Plane surfaces of a horse-shoe magnet

(c) Cylindrical surfaces of a bar magnet

(d) Cylindrical surfaces of a horse-shoe magnet

A coil is wound as a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor 2 and the number of turns per unit length of the coil remain the same, the self  inductance increased by a factor of

(a)  16

(b) 12

(c)  8

(d) 4

Identify the wrong statement describing the color code for carbon resistors.